Drive concepts having optionally connectable and disconnectable driving axles are also referred to as “hang-on”, “on demand” or “disconnect” systems. In particular, a distinction is made between the following drive concepts for motor vehicles. There are motor vehicles with a front engine, in which the front axle is permanently driven, with the rear axle being operable as required. Furthermore, there are motor vehicles having a front engine in the case of which the rear axle is permanently driven, with the front axle being operable as required. Finally, motor vehicles having a rear engine are known in the case of which the rear axle is permanently driven, with the front axle being operable by a hang-on clutch as required.
From DD 10 2008 011 910 A1 a pretensioning unit for a transmission of a motor vehicle is known which permits a friction clutch being operated in the driveline of the motor vehicle. The pretensioning unit comprises a first ramp disc, an annular cage with circumferentially distributed axial openings in which rolling elements are received, a second ramp disc with circumferentially distributed ramp contours, a second ramp disc with circumferentially distributed ramp contours, and an axial bearing. The ramp discs and the cage are form-lockingly axially held together.
WO 2015 120909 A1 proposes a clutch assembly for the driveline of a motor vehicle. The clutch assembly comprises a clutch which can drivingly connect or disconnect the first shaft and the second shaft, a brake by means of which the second shaft can be braked relative to a stationary component, and an operating device by means of which the clutch and the brake can be operated in such a way that the brake is not operated until the clutch has at least been partially opened. The operating device comprises an electric motor and a ramp assembly.
Electromotive ramp assemblies are known. The configuration of the electric motor for operating the ramp assembly depends, inter alia, on the inner friction forces of the ramp assembly.